Aung San Suu Kyi has entered the Burmese parliament to take the oath of office and her seat as an elected member, ushering in a historic new political era after years of oppressive military rule.

The woman who led a nearly quarter of a century struggle for democracy in Myanmar had originally refused to take an oath to "safeguard" the constitution, because her National League for Democracy wants the document amended to reduce the military's dominance of government.

The NLD swept byelections on 1 April but its successful candidates initially refused to take their seats because of the oath dispute. They backed down on Monday but stressed they will push to amend the constitution.

Asked as she walked toward the chamber if this marked an important day for Myanmar, Aung San Suu Kyi said: "I think only time will tell."

The swearing-in ceremony took place in the capital Naypyitaw, which was built by the former army junta. With white roses in her hair, Suu Kyi stood along with several dozen of her party's lawmakers as the speaker of the lower house asked them to read the oath.

The 66-year-old opposition leader's entry into the legislature cements a risky detente between the NLD and the government of President Thein Sein. His government has spearheaded months of unexpected reforms since taking power last year, including the holding of 1 April byelections.

The NLD has too few seats to wield any real power in the ruling party-dominated assembly and there are fears the presence of an opposition could simply legitimise the current regime. But the new MPs are likely to bring a level of public debate to the legislative body that has never been seen as they prepare for the next general election in 2015.

The last time Aung San Suu Kyi's party was set to join parliament was 1990, following a landslide election victory that was swiftly annulled by the army. The military retained outright power until last year.

Aung San Suu Kyi's personal ascent marks an astonishing reversal of fortune for a woman who became one of the world's most prominent prisoners of conscience, held under house arrest for much of the last two decades. When the 1991 Nobel peace prize winner was finally released in late 2010, just after a vote her party boycotted that was deemed neither free nor fair, few could have imagined she would make the leap from democracy advocate to elected official in less than 18 months.

Aung San Suu Kyi and her colleagues had initially refused to join parliament when the latest session began on 23 April because they object to the oath obliging them to "safeguard the constitution". They want the word "safeguard" changed to "respect", but on Monday the leader said they would put the issue aside."Politics is an issue of give and take. We are not giving up, we are just yielding to the aspirations of the people," she said.

The party's failure to take their seats had irked some of Aung San Suu Kyi's backers, who were eager to see her finally take office.

A couple of dozen MPs from smaller opposition parties also sit in the assembly but the vast majority of seats are held by the military-backed ruling party and the army. Changing the constitution require a 75% majority, making it all but impossible without military approval.